<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			*{
				margin: 0;
				padding: 0;
			}
			a{
				display: inline-block;
				text-decoration: none;
				color: white;
				width: 60px;
				height: 30px;
				background: gray;
				text-align: center;
				line-height: 30px;
				border: 1px solid black;
				box-sizing: border-box;
				font-weight: bold;
				
				/*top,height 百分比参照与包含块的高度*/
				/*lefe,margin,padding,width 百分比参照与包含块的宽度*/
				/*translate(-50%,-50%) 百分比参照于自身的宽高*/
				/*background-position 百分比参照于（图片区域-图片的位图像素值）*/
				
				position: absolute;
				left: 50%;
				top: 50%;
				transform: translate(-50%,-50%);
				transition:2000ms;
			}
			
			a:hover{
				background:white;
				color:black;
			}
		</style>
	</head>
	<body>
		<a href="javascript:;">HOME</a>
	</body>
</html>
